Hi Graham,
your wrote:
"This is the case I don't understand. Why would UAs treat all images
without alt the same way that they do decorative images? Given the
image may well be critical to understanding the page, I would expect a
non-visual UA to say something like "graphic [UA-dependent
heuristics]". I would expect a visual UA without image support to
indicate the presence of the image somehow and provide access to some
information about the image."
Take the example of the john's flickr page cited by Ian earlier, that
page contained 24 images without an alt attribute. There is no
reliable means to determine whether any of these images contain
information important enough "critical to understanding the page" to
convey their presence to the user. If all our conveyed in some way,
the user would hear the word "graphic" (for example) 24 times
sprinkled throughout the text content of the page, adding to the
cognitive load on the user without aiding understanding. To get any
information from these images, the user would have to set "virtual"
focus to each one in turn (for example in JAWS, users can navigate
from image to image using the G key) and then use a series of
keystrokes to query the attribute values (src for example). In most
cases the attributes will not contain any useful information, so would
be an exercise in futiltity for the user. As well as taking a very
long time.
does that help?
regards
stevef
On 16/04/2008, James Graham <jg307@cam.ac.uk> wrote:
> Thanks for this example, Steve.
>
> Steven Faulkner wrote:
> > future:
> > <img alt="useful text"> announces "graphic useful text"
> >
>
> In a typical graphical UA without image support this would simply be
> rendered as "useful text" (I see this kind of thing quite often in my feed
> reader, for example).
>
> > <img alt="" noalt> announces "graphic"
> >
> > <img> announces nothing
> >
>
> This is the case I don't understand. Why would UAs treat all images without
> alt the same way that they do decorative images? Given the image may well be
> critical to understanding the page, I would expect a non-visual UA to say
> something like "graphic [UA-dependent heuristics]". I would expect a visual
> UA without image support to indicate the presence of the image somehow and
> provide access to some information about the image.
>
> > <img alt=""> announces nothing
> >
>
> --
> "Eternity's a terrible thought. I mean, where's it all going to end?"
> -- Tom Stoppard, Rosencrantz and Guildenstern are Dead
>
--
with regards
Steve Faulkner
Technical Director - TPG Europe
Director - Web Accessibility Tools Consortium
www.paciellogroup.com | www.wat-c.org
Web Accessibility Toolbar -
http://www.paciellogroup.com/resources/wat-ie-about.html